Irreversible
by Laira Evans
Summary: Eren's final thoughts provoke a different sort of transformation during the invasion of Trost. Instead, he turns into a 12 meter tall version of Mikasa. Unlike in canon, he can't change back. Fem!Titan!Eren.
1. Chapter 1

I don't own Shingeki no Kyojin.

AU notifications beyond the obvious: Mikasa got further out of sight during her suicidal run during the invasion of Trost and Armin was a little slow in finding her after she fell.

Also, for the record, felt the whole "not enough gas to climb the wall" was a little contrived, seeing as they certainly had an awful lot of rope, and 150 feet isn't all that far considering how physically fit they are, but I'll play it according to canon. Wouldn't be the first time in the world a group of people under threat of death failed to realize the obvious.

Chapter One:

'_Where am I?' _I shifted my foot from the smoke as the heat impinged on my swirling thoughts. I stumbled back, body betraying me, and the world shook. My back crashed against a wall, '_no, a building,' _and tiny bricks skittered across the ground below me. I peered into the smoke, now realizing the impossible truth: It was a titan, and yet it was little larger than me. I stood, ever slowly, watching with restrained horror as I rose higher and higher. My eyes reached level with the highest window of the apartment building. How tall did that make me? Twelve, maybe thirteen meters?

That's when I saw her. So tiny, delicate even, though I remembered any number of times she had sent me spinning to the floor in a spar. Clutching a broken blade she stood alone in the ruined street. "Mikasa?" My voice rumbled, low and thunderous, but somehow distinctly feminine. I looked down, somehow accomplishing the impossible in making myself even more shocked than before. Raven-black hair swung at the edges of my eyes, just like Mikasa's. Swinging my face back to the window fast enough to hurt my neck I peered at it's surface, desperate to capture every detail. My fingers trailed across my cheeks, testing the vision that my eyes could not believe. '_This is me?' _But it wasn't my face at all, it was hers.

"Wh-what happened to me? Where's Armin?" The last thing I could remember was... was jumping into a titan's mouth to save him. He'd bitten off my arm, so why wasn't I dead? I should be dead, shouldn't I? People didn't just wake up thirteen meters tall looking like their best friend after being swallowed by a giant. I didn't even look like a titan. That, at least, might have some logic behind it. Might hold the secret of how titans actually produced. Instead, I looked human. Just... very, very tall. My knuckles ached, as if I had punched something with all my strength. Had I killed that titan with just my fists during some sort of blind rage?

"Eren?" Her voice was so soft I could barely hear it.

"Mikasa, what happened to me?" I bent towards her as I spoke, but recoiled as I saw a flash of fear contort her face. She recovered almost instantaneously, strong as always.

"There's no time for this now. We've been cut off from our resupply point. We don't have enough gas to climb the wall and the trainees I sent to take back the headquarters will be slaughtered without my help. You need to carry me."

"R-right." I didn't dare grab her for fear of crushing her, but instead lowered my hand to the ground, palm up. Athletically springing on top, she grabbed ahold of my thumb that was now about the same size as her thigh. Might right hand clutched at roofs as I started us on our way, half shattering them as I pulled at them for balance. "I think I'm starting to get the hang of this." My steps grew more sure, and soon I wasn't walking but running, ground flying beneath us.

"You had better. We won't get inside without a fight." That was understating things. I was close enough now to see a depressingly small group of fighters swing into the top floor of HQ, but surrounding the building was a group of titans of all sizes. "Hey, stop for a second." I halted, stumbling slightly as I tried to account for the changes in momentum and my center of gravity. "Grab that. If you're going to walk around with my body I'd prefer that you show at least a little modesty." She gave a hesitant smile, obviously as disturbed with my transformation as I was. I grabbed the two giant flags from the mayor's mansion, tying them around myself with a blush. I grabbed the flagpole too for good measure. Considering the state of my knuckles, I'd rather not beat on too many more barehanded if I could help it.

The stop for something as simple as modest could be considered criminal, given the circumstances, but we were both far from being calm. The clothing, as simple as it was, was a touch of normality to keep us both sane. I looked different enough from the titans that other humans might hesitate before attacking me, but I was obviously not human. Still, I didn't have the hideously stretched mouth of normal titans, though like them I felt somewhat lighter than I should if I were made entirely from flesh and bone. My knuckles, too, were already visibly healing, though at nowhere near the rate of a true titan.

Apparently the other titans felt I was different as well, as several stopped heading for the HQ castle in favor of chasing me. "Dodge them," shouted Mikasa, struggling to be heard. "I need to get inside before anything else." It was easier said than done. The three to five meter class were little difficulty, as they hardly came up to my knees. They couldn't come close to matching my speed, and even in the mass of them their small arms did little to detain me. The seven meter class was more worrisome. The size of children – ugly, apelike, flesh-eating children – they had enough mass that one good grab could send me sprawling. I leaped upwards over a trio of them, feet coming level with the roofs as Mikasa held on for dear life. It was during my brief flight that I noticed the next obstacle.

I ducked under his arm as he swung at me, but another stood right behind him, blocking my way. Both were a full three meters taller taller than me with limbs as thick as my waist, their features a brutal caricature of humanity. The horde of smaller titans was swiftly approaching my back, but suddenly I found myself wondrously, gloriously unafraid. This was what I had trained for, this was the threat I'd dedicated my life to eradicating. It didn't matter if I was a twelve meter tall girl, so long as it helped me be free, to break free of the gilded cage that had trapped humanity for a hundred years.

"Hold on tight." I jumped upwards, rolling up and over the building to the right of us. Tiles shattered from my passage, prickling against my skin. I had no time to spare for pain, but my gambit had worked. The way was clear, and with a renewed burst of speed I sprinted for the castle, titans howling their outrage behind me.

"Look out!" I spun, flag pole sweeping out to catch the deviant flying through the air at me. It was the same fifteen meter monster that had eaten Thomas. The pole was just enough to send him off course to smash through a building, but he took my improvised weapon with him.

"Damnit!." Fury rose within me, my free hand clenching into a fist as I considered rushing into the crushed building to finish him off. To my regret, there was no time. It looked like every titan in the town was coming after me now, so I was forced to grit my teeth and keep going. Two more titans a little larger than me were digging their hands into the tower, but fortunately they were too distracted to go for me at the moment. Climbing onto the first level of the castle I reached up to place Mikasa in the highest window.

"Eren, distract them if you can for ten minutes. I'll be back out soon to help you."

"Right." She disappeared in a flash, headed to places she could not follow. I hoped she faced less of an opposition inside than I did out here.

Jumping down, the shock wave sent small titans stumbling. I took the opportunity to punt each of them flying as they rose to their feet. One particularly brutal kick that left my foot stinging was just enough to rip off a 7-meter's head. I darted forward to give him the coup de grace but a pair of his fellows drove me back. "This isn't going to work." Already the one I had felled was regenerating, and the 15-meter monstrosities now arriving were stronger than I was, even if I had an advantage in speed. I could take one of them on, maybe two, but if I stayed here much longer I'd be overwhelmed in short order.

Looking around me to guard against being cornered I saw it, a speck of yellow against the red roofs. "Armin?"

* * *

Shingeki is absolutely amazing, it's a shame its plotline is so perfect that it's difficult to write fanfics of. Harry Potter on the other hand, well, I think anyone sane admits that those books had more holes than the bogs outside Mordor.


	2. Chapter 2

Chapita Tu-oo.

He was swinging through the streets towards the castle, moving faster than I'd ever seen him go in training. I could already tell it wouldn't be enough. There wasn't time enough to make any real plans, so I just leapt in among the horde, hand outstretched to catch him before they did.. The smaller titans were like embers against my side as they cushioned my skidding fall. "**Owe!**" My voice thundered as I shook him reflexively, his blood-covered blade dropping to the cobbles below. By the sound of his screaming I deduced that at least I hadn't accidentally broken his neck by shaking him like that. Kicking off the chest of a 15-meter class I rolled backwards and up onto my feet, sprinting several hundred yards away before I halted. "Armin, it's me, calm down already. And you damn well better not cut my hand again."

"Mikasa? Is that you?"

Well, I couldn't really fault him for the guess, considering the circumstances. "The others are refilling their tanks, we need to distract the titans until they finish." He said nothing, mouth still agape. "Armin, focus! Do you have any ideas?" I was strafing right to keep as many of them following me as I could, but the situation was growing worse and worse.

"Umm, grab those bricks, if you hit them it should slow them down."

I was hoping for something a little more flashy but it would have to do. Gathering up rubble from a ruined building I started pelting them with the stones. Nearly as powerful as canon balls thanks to the strength of my arm they whistled through the air and sent titan flesh flying. It was just barely enough to keep the 15-meter titans stumbling, and even walking backwards I could outpace most of the smaller titans. Through a gap I caught a glimpse of the destroyed gates. The titans were still coming through, a seemingly endless horde. '_Mikasa, where are you?'_

_ * V * V *_

"Mikasa! Wake up Mikasa!"

'_?' _My head was pounding, my back a mass of pain. Where was I? Someone was looking for Mikasa? I brought my hand up to rub at my eyes. "Armin? Why are you so tiny?"

"Get up, Mikasa, he's right behind you!"

I started to rise just as a house-sized hand pinned my shoulder to the ground. The titan's jaws opened wider and wider, until they could encompass my whole head. '_Shit' _I made to swing back onto my shoulders and kick him away but a 3-meter class sank his teeth into my calf, disrupting the movement. "Armin, get out of here, I can't hold them." I kicked the titan away, but two more replaced it. It was taking all my arm strength to hold the 15-meter titan still pinning me to the ground. It appeared that I was going to be devoured a second time. This time around I suspected it would take more than one bite.

Suddenly the titan went slack, weight slowly dissipating into hot smoke. I pushed its burning corpse to the side with both hands, Armin having climbed to my shoulder. "Come on, we need to go."

There, hair swaying as she perched on the roof, was Mikasa. "You made it just in time, where are the others?" I punched away the two on my legs, wincing at the divots they made in my flesh. They were only bleeding a small trickle, however, and appeared to already be healing, though slowly.

"They went on ahead."

"But, how are you there?" Armin was considerably confused, it took me a moment to remember why.

"I'm not Mikasa, I'm Eren."

"...Right."

Mikasa swung down, neatly killing a medium-sized titan coming from in front of us as we started to run. I kept to just a fast walk, not wanting to press Mikasa too hard or send Armin flying off my shoulder from jogging. After the kill she landed deftly on my waiting hand.

"Guys, where are we going, exactly?" asked Armin. "They'll have closed the gate by now, and Eren can't climb the wall with us."

I faltered a step but kept going. "At least I can get you two to the wall. I'll figure out something after that."

"I'm not leaving you Eren. I'll kill every last one of them if I must." With Mikasa, I half believed she could do it.

A blast came from in front of us, an unholy roar shouting triumph. The gate was destroyed. "**No.**" Pebbles jumped at the sound of voice. "**No, not again. Not this time.**" I'd stand at the broken gate and defend it myself if no one remained to stand with me. I wouldn't let humanity end here.

I was sprinting before I knew it. "...ren, Eren!"

"What is it Armin?"

"You can't fight them head on, you're not strong enough. "My vision flashed white with rage as I remembered Hannes saying the same just after my mother died. I was always too damned weak, wasn't I. "You need to draw the titans away long enough for reinforcements to arrive. You're like a magnet to them, we've already got at least twenty of them following us." He was right. And with the other trainees fleeing and the scouts dead, that number was only increasing.

"...Alright Armin. We'll do it your way." I wasn't that much faster than them when I wasn't sprinting, so I couldn't just turn around immediately. I took a curving path past the broken inner gates gate, careful not to go too close however much I wanted to. If the titans started sensing the humans behind the wall instead of me then this entire plan would fall apart. "Hold on." I picked up some more rubble, Armin and Mikasa holding onto the flags that were my clothing as I bent for them. Now that I was armed, I could slow down, at least a little. A few good throws sent the sprinters among them hurtling back into the pack. The rest were easy enough to lead. I stayed just a few dozen meters ahead of them, not wanting to lose them.

"Mikasa, keep an eye out for deviants, one caught us earlier," said Armin.

"Hn."

With them as my lookouts, I was free to lead the pack like some sort of reverse sheepdog. I was growing ever more adept with this body, no longer having to keep an eye on my feet to maintain my balance. Unfortunately, here came the hard part. "I'm going to take them through the outer gate. You both need to climb the wall."

"I'm not leaving you," said Mikasa.

"If I get caught in there you might not make it out." I turned my head towards my shoulder, glaring sternly at that tiny mirror of my new face. "They'll need your skills at the inner gate if this fails." There was no time for further argument, so I picked up one in each hand as we came to the massive hole the colossal titan had knocked in wall. Even as tall I now was, it was still twice my height and several times my width. As I reached the entrance I tossed them upwards, Mikasa shouting in protest. Their 3-d gear _snicked_ out a moment later, anchoring them high above the reach of the titans. As I had feared, the way was not clear.

"I've faced worse odds." An alien instinct hold of me as I charged, a roar to shake stone blasting from my throat unbidden. The titan's weight shifted to his back foot and I took advantage, shoving him to the ground. A quick spin sent me clear of the grab of an ape-faced 7-meter class. I slapped the wall, transferring the momentum of my spin into forward movement. A moment later I was free. I could see the sky again, stretching on forever. I stood in the Outside that had once been Inside, a part of the domain of humans. And now, looking across the field that should have been ours, was a herd of titans. My grin at seeing the sun disappeared as quickly as it came.

"Eren, up here!" I laughed, Mikasa had saved me again. Aiming for the left side so that my hands wouldn't crush him I coiled my body like a spring. The jump that followed was one worthy of Mikasa herself, first in our class. I gripped the edge of the narrow cannon platform above the gate. The wall pushed out a bit to either side, so I was able to swing my feet to get purchase on the wall face to the left of me. From there it was just a matter of levering myself up onto the ledge.

"Go help them, Mikasa, I've got it from here." And like a flash, she was gone, likely dragging Armin along with her. It wasn't quite as quick as a straight path, but they could reach the rest of the army in safety from here just by walking on top of the wall.

I was alone. Save for the milling titans beneath me, at least. The ledge was narrow, certainly not meant for someone the size of a titan. My feet didn't quite fit, and even with my arm bracing me against one side of the cubby it constantly felt like I was just about to fall. I had no real fear of heights, but of being devoured when I fell? If I was honest with myself, there was at least an inkling. Looking down, there really was so damned many of them, weren't there. Giant mouths, always hungry. I would have thought being roughly their size would ease some of that fear. Instead I just kept thinking that the end would come a lot slower as piece by piece I was eaten alive...

* * *

End chapter 2:

-The Use of Tools.

Err, question for canon fanatics. The scene in the manga where the titan learned/relearned how to climb trees, was there any indication from point of the sun in sky or something just how long that took? Please and thank you.

To the reviewer who questioned my use of first person in telling this story: I actually got two paragraphs into the first chapter before I wondered, "Why am I writing this in first person, anyways?" Then I figured I'd just go with it. Gives a more personal feel for Eren, even if it is at the expense of some insight into the primal fear the others have of something so terribly huge. Might throw in some brief entries from other characters later though. Besides, without a forty page setup it's difficult to get the same feeling as you'd get from a 20-second sketch in the anime of that raw ferocity Eren displays.

Whew, wrote this in one sitting.


	3. Chapter 3

Chapiter thres:

My hand was starting to ache from gripping the wall for so long. Had the plan worked or was there simply too many of that had failed to follow me? Maybe the general hadn't believed Mikasa and Armin – after all, who would under the circumstances – and had ordered a retreat. I could be the only human (ish) within ten miles of here by now. All alone, save for the squirming horde below me. They were like a pile of writhing worms, each one climbing on another to reach their prize. And reach me they would, given time. The mound of titans was growing higher as more came from the fields beyond the wall. One of them even tried to shimmy up the rectangular support wall sticking out to the side of the hole.

Amazingly, he actually had some degree of success. His hands were smoking, constantly regenerating from the strain of holding onto the smooth surface. I'd ripped free a canon and thrown it at him the first time I saw it happening, but I only had one left within reach. I really didn't trust my balance yet on such a narrow ledge to try and reach for the ones further away. Unfortunately this meant that I was forced to watch as he slowly progressed upwards towards me, I couldn't afford to throw my last projectile early. I just hoped none of the others picked up on the idea.

I spoke too soon. The climber wouldn't be the first to reach me and pull me into the swarm after all. The titans on the bottom had apparently been pinned down well enough that the ones on top were no longer losing their footing. The 15-meter class reached out, his grip the same as death. I threw the cannon at him, but the wheel hit first. It was just a glancing blow to his head, and he was still standing. Another twenty seconds and he would reach for me again.

No, this wouldn't do. "I refuse to die in a cage." Not caged by walls, the preaching of sheep, or by my own fear. It was almost time, but I wouldn't falter. If I was quick, and rolled well when I landed, I might be able to break free. From there... I'd work out something.

"Eren, are you alright?" My guardian angel, just in time.

"Not if you don't hurry." Though to be honest, with so many, even her aid wouldn't be enough for long.

"This beast is what you brought me here to see? Load the canons, I want it off my wall."

Mikasa's blades sang as she slowly drew them out. "My specialty involves the cutting of flesh. Any who care for a demonstration need merely step closer."

I could only catch a few snatches of the ensuing chatter, but I could tell it was leading nowhere good.

"You bear the same face... you're in collusion with it aren't you. There is only one sentence for a traitor to humanity. Kill her." Muskets clicked as they readied to fire.

"**NO!**" I roared, wishing I could crush that paranoid fool from existence.

"That's enough, put your arms down."

"Pixis!" It was too soon, I feared, but I felt a flicker of hope. I knew that name, even if I didn't know his face. General of the defenses for the entire southern region, in the case of a breach his authority rivaled that of the king.

"This young man has been filling me in on the situation. It would be poor thanks to kill the trainee that prevented the fall of Wall Rose." He walked to the edge so that I could just see his face as he leaned over the side. "I always thought I wouldn't mind so much being eaten by a titan if it was a breathtaking beauty."

'_…Crazy old man.'_

"Major, find some ropes and winches big enough to hall her up. Start shooting the others, we can't let them pile up any more than they already have."

"Quickly, please!" I shouted up at them. The titan on top was still a little unsteady so his first two grabs had missed by a fair margin, but it was only a matter of time. "There's still two canons to the left of me." The ones on top of the tower had been destroyed by the colossal titan, but as I recalled there were still a few on the level above me as well, provided they could shoot around me.

A few shouted orders later and a number of guardsmen rappelled down, muskets still in hand. Mikasa touched down lightly on my shoulder. I could tell she was still looking out for some sort of double-cross. It appeared they would be true to their word, however. A flurry of musket balls shot past me, blinding the nearest titan. Provided nothing else went wrong, explosives should be enough to deal with the rest, expensive though it would be. Trost was abandoned, the inner gate presumably blocked off or soon-to-be, so hopefully there were no other humans in range to draw them off. It would be like shooting fish in a barrel.

Armin came down next, landing beside me on the platform. He look up at me, then suddenly backed away and turned to look at something else. Strange. "Thanks for the save, Armin. How did you manage to find Pixis, anyways?"

"I recognized him from one of the textbooks. I'm surprised he believed me though."

"You don't give yourself enough credit."

He stood unnaturally still. "Eren, I'm sorry I froze. You saved me from that titan, I'm the reason this happened to you." He started to tear up.

"I don't regret it Armin. Besides, some good came of it in the end."

There was silence for awhile besides the intermittent firing of the remaining canons. Then Mikasa whispered in my ear, "I think he turned around like that because he saw a little too much. You might want to find a little more to wear once we get back over the wall." The next hour of waiting was a little hazy after that shocking revelation.

* * *

Just a short chapter this time. Need to go cook a blueberry pie.

The way I think about it, the titans aren't that different from the AI in World of Warcraft before the bugs got fixed. If you just use the terrain, you should be able to confuse 90% of them quite easily. The problem is that there's hardly anything big enough to count as a significant terrain barrier to a creature 45 feet tall.

Also, that guy who wanted to shoot Eren apparently doesn't have a name in canon despite having 6 lines. I looked. He deserved a name though, that guy was awesome.


	4. Chapter 4

Even after they lowered the ropes and let me on top of the wall it was several hours before I was allowed to move. I sat after awhile, legs hanging over the edge as I plugged my ears against the larger explosions. Slowly but surely the horde was worn down, with particular attention given to the three that had learned how to climb. A couple deviant titans just ran through the gap, but despite whatever interference they may have caused word came shortly before sunset that repairs at the inner gate were completed. It was a slow march back along the wall. The way was narrow, barely the width of my shoulders, leaving no room for any to walk beside me. Guardsmen stayed ahead and behind me, however, at least a dozen muskets trained on me at all times. Armin appeared to be taking notes down as he walked behind Pixis and several others. Mikasa was still on my shoulder, staying silent during the walk. I was forced to take short, slow steps. I was so convinced that I wasn't really moving at all that I was half-surprised to finally reach the end of Trost's barrier wall.

I was a little disappointed to see the state of the inner gate. "Pixis," I said, though for a smaller entity it would be a shout. "You've walled it off completely, aren't you planning to retake Trost?"

"In time," he called without even turning to face me, apparently quite at ease with having someone the size of a titan standing twenty meters behind him.

'_In time...'_ It would have to do, though it pained me to give up even an inch of ground to them. Just then a man swung up from the side of the wall, landing neatly in front of the procession. It was difficult to judge properly my perspective, but he seemed rather on the short side.

"Corporal Rivaille, you've arrived." Given that smoke still rose from the abandoned Trost, Pixis seemed entirely too cheery, new arrival or not.

"General Pixis, that's quite the pet you have there." Mikasa bristled at that comment, grip tightening on a strand of my hair.

"She's quite the change from the ordinary titan isn't she," said Pixis.

"Dogs may look different than wolves, but they can still bite their masters when not fed. I wonder what this one eats." Did he really just call me a dog? It sounded like he was trying to bait me, but who in their right mind would taunt someone seven times their size? If I was still... still his size, I wouldn't put up with it. Then again, he was a corporal. Insults from those above you in the military were like rain: too frequent, and of little weight. "Regardless, it would be unwise to bring it to the main army. A quarter fled when the armored titan broke through, and the rest took heavy losses. Bring a titan into their midst and they're likely to mutiny."

"Hmm... I thought the same. Are you capable of taking custody of her at the Scouting Legion's headquarters until I send word?"

"I will see it done," said Rivaille. "It will be no trouble to kill her if she attacks. My team is arriving as we speak." Despite being so small, there was a weight about him that made me wary of his words.

"How dare that shorty," mumbled Mikasa.

"See that it doesn't come to that," said Pixis. "Give her whatever she asks for, within reason. There is a secret here that she may be the key to."

I stayed still as the rest of the procession cautiously made their way past my feet. Armin called back to us as he left, "I'll come to see you as soon as I can." The parting felt odd. It had years since I'd been more than a few hundred meters from Armin. Still, even knowing his strength of spirit, I knew he'd be of more use as the General's aide than fighting in the front lines.

"Well come along then." I turned, surprised to see that Rivailles team had arrived. These were no rookie trainees. They were as light on their feet as Mikasa and had stances similar to Annie's, as if they were on the edge of doing violence. These, then, would be my jailors. Well, a few hours ago I thought I was to be eaten, or perhaps slain by a cannon ball. From that point of view it was still a step up, though certainly not the promotion I had hoping for when this mess all began. Though, looking at it one way, I actually had managed to join the Scouting Legion.

* * *

End chapter 4: Little depressing to switch to this from the Naruto genre. Went from 2000+ views per chapter to 100. Well, anyways, this kicks it up to the 5000 words mark, good point to pause. Probably be a few days for the next chapter (the chapter a day streak ceases), but it should be at least triple this length.


End file.
